VSE editing different frame rates
If you can, just separate both into two separated scenes rendered at different frame rates. This will be the case if your final footage doesn't change too often (ideally, one time).

If the amount of footage is manageable, use the speed control effect strip to make both the same speed.

Otherwise, put all your raw 25fps into one large edit and render it at 24fps. Now you can import it into your actual project and edit it like the rest of the video.